1. Field of the Invention
The present invention relates to the papermaking arts, and specifically to the manufacture of paper tissue and toweling, which may be collectively referred to as bulk tissue. The present invention also relates to the manufacture of nonwoven articles and fabrics by processes such as hydroentanglement. In particular, the present invention relates to belts, which have had a functional polymeric resin material deposited in precise preselected areas onto their base structures to fill those areas and, when desired, to form a layer of desired thickness thereover. Belts of this type are used in the manufacture of bulk tissue and towel, and of nonwoven articles and fabrics.
2. Background of the Invention
Soft, absorbent disposable paper products, such as facial tissue, bath tissue and paper toweling, are a pervasive feature of contemporary life in modern industrialized societies. While there are numerous methods for manufacturing such products, in general terms, their manufacture begins with the formation of an embryonic paper web in the forming section of a paper machine. The embryonic paper web is then transferred to a through-air-drying (TAD) fabric by means of an air flow, brought about by vacuum or suction, which deflects the web and forces it to conform, at least in part, to the topography of the TAD fabric. Downstream from the transfer point, the web, carried on the TAD fabric, passes through a through-air dryer, where a flow of heated air, directed against the web and through the TAD fabric, dries the web to a desired degree. Finally, downstream from the through-air dryer, the web may be adhered to the surface of a Yankee dryer and imprinted thereon by the surface of the TAD fabric, for further and complete drying. The fully dried web is then removed from the surface of the Yankee dryer with a doctor blade, which foreshortens or crepes the web and increases its bulk. The foreshortened web is then wound onto rolls for subsequent processing, including packaging into a form suitable for shipment to and purchase by consumers.
As noted above, there are many methods for manufacturing bulk tissue products, and the foregoing description should be understood to be an outline of the general steps shared by some of the methods. For example, the use of a Yankee dryer is not always required, as, in a given situation, foreshortening may not be desired, or other means, such as “wet creping”, may have already been taken to foreshorten the web.
The present application is concerned, at least in part, with the TAD fabrics used on the through-air dryer of a bulk tissue machine. Historically, TAD fabrics were woven from monofilament yarns in weave patterns which provided their paper-supporting surfaces with knuckles, elevated relative to other areas on the surfaces, having relatively long floats. Upon transfer from a forming fabric to the paper-contacting surface of such a TAD fabric, the embryonic paper web would assume, at least in part, the topography of that surface. As a consequence, the portions of the embryonic paper web deflected between the knuckles becomes less dense relative to those on the knuckles, ultimately giving the bulk tissue product softness and absorbency. Upon subsequent pressure transfer from the TAD fabric to the surface of a Yankee dryer, the knuckles on the paper-contacting surface of the TAD fabric imprint and densify those portions of the paper web lying thereon. This densification, in turn, strengthens the bulk tissue product as a whole. The densification was typically enhanced by abrading or sanding the paper-contacting surface of the TAD fabric to provide the knuckles with flat surfaces, thereby increasing the contact area between the paper web and the Yankee dryer, and enlarging the knuckle imprints to strengthen the bulk tissue product further and to dry it more completely.
Driven by consumer interest in softer, more absorbent and stronger bulk tissue products, development initially centered on the weave patterns used to produce TAD fabrics. For example, in the now expired U.S. Pat. Nos. 4,191,609 and 4,239,065 to Trokhan, which are assigned to the Procter & Gamble Company of Cincinnati, Ohio, TAD fabrics woven in weave patterns having nonnumerically consecutive warp-pick sequences are shown. The disclosed weave patterns provide the paper-supporting surfaces of the subject TAD fabrics with a plurality of wicker-basket-like cavities disposed in a bilaterally staggered array, each such cavity being bounded by knuckles on the top-surface plane of the fabric. The TAD fabrics enable a bulk tissue product, having a patterned array of relatively closely spaced uncompressed pillowlike zones, each zone being circumscribed by a picket-like lineament comprising alternately spaced areas of compacted fibers and relatively non-compacted fibers and formed by the top-surface-plane knuckles, to be produced.
During the 1980's, an alternate means for providing a TAD fabric with the equivalent of wicker-basket-like cavities was developed. Procter & Gamble's U.S. Pat. Nos. 4,528,239; 4,529,480; and 4,637,859 to Trokhan, which are among the earliest U.S. patent documents on these means, show a TAD belt comprising a foraminous woven element, that is, a woven base fabric, having a coating of a polymeric resin material in preselected areas. More specifically, the polymeric resin material provides the TAD belt with a macroscopically monoplanar, patterned, continuous network surface which serves to define within the TAD belt a plurality of discrete, isolated deflection conduits or holes, rather than wicker-basket-like cavities. To produce the TAD belt, the foraminous woven element is thoroughly coated with a liquid photosensitive resin to a controlled thickness above its upper surface, and a mask or a negative having opaque and transparent regions which define a desired pattern is brought into contact with the surface of the liquid photosensitive resin, and the resin is exposed to actinic radiation through the mask. The radiation, typically in the ultraviolet (UV) portion of the spectrum, cures the portions of the resin exposed through the mask, but does not cure the portions shadowed by the mask. The uncured resin is subsequently removed by washing to leave behind the foraminous woven element with a coating in the desired pattern formed by the cured resin.
The seminal U.S. patent disclosing this method is Procter & Gamble's U.S. Pat. No. 4,514,345 to Johnson et al. In addition to disclosing the method for making the TAD belt described in the preceding paragraph, this patent also shows a belt in which the polymeric resin material forms a plurality of discrete protuberances on its surface. That is to say, the pattern is the reverse of a continuous network having holes. Instead, the pattern is of discrete areas which are occluded or blocked by the polymeric resin material in an otherwise open foraminous woven element. Belts of this kind may be used in the forming section of a bulk tissue machine to form embryonic paper webs having discrete regions of relatively low basis weight in a continuous background of relatively high basis weight, as shown, for example, in Procter & Gamble's U.S. Pat. No. 5,277,761 to Van Phan et al. Belts of this kind may also be used to manufacture nonwoven articles and fabrics, which have discrete regions in which the density of fibers is less than that in adjacent regions, by processes such as hydroentanglement. Also in U.S. Pat. Nos. 6,080,691 and 6,120,642 to Kimberly-Clark there is disclosed a papermaking fabric for producing a soft, bulky tissue web wherein the web contact surface is a three dimensional porous nonwoven material. This material may be in the form of fiberous mats or web, extruded network or foams. Attachment of the porous nonwoven material can be by lamination, extrusion, adhesives, melt bonding, entanglement, welding, needling, nesting or layering.
In addition to discrete (non-continuous) and continuous networks of polymeric resin material on the foraminous woven element, the method disclosed in U.S. Pat. No. 4,514,345 to Johnson et al. may also be used to manufacture belts having semicontinuous networks of polymeric resin material. For example, Procter & Gamble's U.S. Pat. No. 5,714,041 to Ayers et al. shows a belt, useful as a TAD fabric, having a framework of protuberances arranged in a semicontinuous pattern to provide a semicontinuous pattern of deflection conduits. By “semicontinuous” is meant that each protuberance extends substantially throughout the belt in an essentially linear fashion, and that each protuberance is spaced apart from adjacent protuberances. As such, the protuberances may be lines which are generally straight, parallel and equally spaced from one another, or may be in the shape of zigzags which are generally parallel and equally spaced from one another.
In some bulk tissue applications, press fabrics having a continuous, semicontinuous or discrete network of polymeric resin material on their paper-contacting surfaces are used. By “press fabric” is meant a fabric normally used on the press section of a paper machine and comprising a base fabric or other support structure and one or more layers of staple fiber material attached to at least one side thereof. For example, Procter & Gamble's U.S. Pat. No. 5,556,509 to Trokhan et al. shows “press fabrics” having continuous and discrete networks of polymeric material on their paper-contacting surfaces and used to make bulk tissue products.
The method disclosed in U.S. Pat. No. 4,514,345, and the refinements thereto disclosed in subsequent Procter & Gamble U.S. patents, are quite elaborate and time-consuming. A more direct approach for providing a forming, press or TAD fabric, or a fabric used in the manufacture of nonwoven articles and fabrics by processes such as hydroentanglement, with a coating of a polymeric resin material in the form of a continuous, semicontinuous or discrete network has long been sought in the industries concerned. The present invention satisfies this long-felt need.